I believe this is a great model to test various settings.
In the picture with all 4 turtles, the top left is no ironing and no adaptive layering. Bottom left is top ironing only. Bottom right is adaptive layering only. Top right is adaptive layering and top ironing.
The two turtles using adaptive layering, you can tell where the speed changes due to discoloration on the sides and the top ironing plays a role in that top shell smoothness.
This is a great print to play around with these types of settings and clearly seeing the differences.